The present invention relates to a radio communication system and method and, particularly, to a radio communication system and method making it possible to introduce a system utilizing RFID (Radio Frequency IDentification) technology into a radio network environment.
Lately, systems utilizing RFID attract attention and have begun to be applied for various uses. A basic configuration of a system using RFID includes an RFID reader/writer that performs data communication with an RFID radio tag via radio and a computer terminal that controls the RFID reader/writer. The RFID reader/writer can read data stored on the radio tag or write data into the radio tag (see Non-patent Document 1).
An RFID radio tag does not have a built-in battery, since it generates a power supply voltage using radio waves when transmitting and receiving data to and from the RFID reader/writer. Such a radio tag is generally called “passive-type”. Specifically, in the RFID radio tag, a radio wave (a part of a carrier) supplied from the RFID reader/writer is rectified from AC to DC by a full-wave rectifier. The DC voltage is stepped up or down to a suitable voltage as a circuit power supply by an internal voltage control circuit or a booster circuit, and then the power is supplied as a power supply to internal circuits such as a current mode demodulator and a logic circuit. In this case, the efficiency of AC to DC conversion in the RFID radio tag can be enhanced by optimizing the size of a PMOS/NMOS rectifying diode included in the full-wave rectifier or reducing a loss due to parasitic capacitance or the like before input to the rectifying diode and a loss due to mismatch between an antenna and an input of the rectifier.
A technology concerning an indoor intruder detection apparatus is disclosed in Patent Document 1. The indoor intruder detection apparatus disclosed therein includes a transmitting device, a receiving device, and an alarm device. The transmitting device transmits an unmodulated radio signal with a given carrier frequency. The receiving device includes a receiving unit that receives a signal output from the transmitting device, a detecting unit that detects the received signal, and a level fluctuation detecting unit that outputs a detection signal when the level of the detected signal exceeds a predetermined range. The alarm device sounds an alarm based on the detection signal output from the level fluctuation detecting unit of the receiving device. The indoor intruder detection apparatus disclosed in Patent Document 1 detects an indoor intruder based on a fluctuation in the received electric field of radio waves output from the transmitting device and a fluctuation in the bit error rate of demodulated signals.